In a 1.times.N optical switch, a single optical fiber forms an optical path with an optical fiber selected from N optical fibers. Therefore, a signal propagating along the single fiber will be coupled into one of the selected N fibers. Similarly, a signal propagating along the selected fiber (in the opposite direction) will be coupled into the single fiber. A switching arrangement is required to assist in the selection for the one-out-of-N fibers.
In electromechanical 1.times.N optical switches, the switching operation is effected by the movement of an end of the single fiber relative to the ends of the N optical fibers. To form an optical path, the end of the single optical fiber is aligned with the end of the selected fiber from the N fibers. In such systems, alignment of the fiber ends is critical and much precision is required with the electromechanical drive devices, such as motors and their movements, to ensure accurate and reproducible alignment of the single fiber with each of the n optical fibers. Nonetheless, performance of such switches has remained poor with use restricted to multimode optical fibers. In present day optical networks, it is often desirable to use single mode fibers, not multimode fibers.
An exemplary prior art 1.times.N switch that has allowed for the use of single mode fibers is disclosed in U.S. Pat. No. 5,359,683, issued to J. Pan on Oct. 25, 1994. In this arrangement, a set of GRIN lenses, disposed between the single fiber and the N fibers, is used to ameliorate the effects of misalignment and provide better coupling between the single fiber and the selected fiber. While considered an improvement, the arrangement is difficult and expensive to manufacture, requiring individual stepper motors to align each GRIN lens with the selected fiber.
A need remains, therefore, for a 1.times.N optical switch, suitable for use with single mode fibers, that is relatively inexpensive to manufacture, yet provides the needed alignment between the single fiber and the selected one-out-of-N fibers.